Short wave detector system



Aug. 11, 1936.

R. A. BRADEN SHORT WAVE DETECTOR SYSTEM Filed Jan. 17, 1935 U'I'ILIZH'T'ION CIRCUIT CIRCUIT HNTENNH 2 WW/w INVENTO ReneH.Braden t ATTORNEY P0 WE R SUPPLY HIGH VOL'I'R GB Low V POWER sui PLY embodiment thereof.

Patented Aug. 11, 1936 PATENT or ies SHORT WAVE DETECTOR SYSTEM Rene A. Braden, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 17, 1935, Serial No. 2,141

9 Claims.

This invention relates to ultra short wave receiving apparatus and has particular reference to means for detecting the received radio frequency energy.

It is well known that an electron tube may be so constructed asto operate efliciently when its grid is maintained at high direct current potential in relation both to the cathode and to the plate.

Difiiculties have been encountered, however, in using two such tubes in push-pull relationship because of the exacting requirements imposed upon the tubes themselves and upon the external connections for obtaining a suitable impedance match between different portions of the system.

In order to overcome this difficulty, have found it desirable to include within one envelope two complete sets of triode electrodes and to provide a suitable dipole antenna connected to my twin-element detector tube through a symmetrical tWo-wire transmission line having means associated therewith for obtaining standing waves with loops of energy centered in each of the sets of triode electrodes.

Accordingly, it is among the objects of my in- Another object of my invention is to provide apparatus of the class hereinbefore mentioned in which the balancing of impedances in different portions of the system may be greatly facilitated.

Another object of my invention is to provide suitable tuning devices in association with a two-wire transmission line whereby an electron discharge tube having two sets of triode electrodes may be operated as the equivalent of two .Barkhausen-Kurz tubes when connected in a push-pull manner.

The foregoing and other objects of my invention will be more fully understood upon reference to the ensuing detailed description when read in connection with the accompanying drawing, in which Figure 1 shows diagrammatically one embodiment of my invention; and

Fig. 2 shows also diagrammatically another Referring to Fig. 1, I- show an electron discharge tube of special construction having an envelope I within which are mounted two cylindrical anodes 3, two grids 5 and two filaments Each. of the triode sets of electrodes may be so constituted as to operate in the manner of a Barkhausen-Kurz tube, that is to say, with a high direct current potential impressed upon the grid and with a small difference of potential between the cathode'and the plate suchras to 6 bias the latter either positively or negatively, according to circumstances.

In the embodiment shown in Fig. l, the two plates 3 may be mounted adjacent one another. The plate lead 8 is, therefore, conveniently made 3) common to the two plates. This lead is shown connected to an external circuit which includes an adjustable tap 2! on a potentiometer 23 the voltage drop across which'rnay be derived from a low voltage power supply '25, the latter being if? also connected to the two conductors ill of a Lecher-wire system comprehending in one part thereof the filaments l. The grids 5 are also connected in parallel through a lead 19 to a circuit which includes the primary 9 of a suit- 20 able transformer l i and thence to a tap 13 on a potentiometer i5 across which a high direct current voltage may be impressed from any suitable power supply such as that represented at ll. The secondary of the transformer H may 5 be connected to any desired utilization circuit.

Connections between the low voltage power supply and the Lecher-wire system may include a rheostat '29 and two radio frequency chokes 3|, one in each lead. The conductors 0 27 are preferably disposed quite close to and parallel with one another. As they enter the envelope of the tube, they diverge sufficiently to permit of running the filaments each exactly through the center of its triode system. The filament leads again converge so as to be brought out at the top of the tube into an extension of the Lecher-wire system indicated at 33. A bridging member 35 is adjustably connected across the conductors 33 in such manner that tuning of the circuit may be accomplished. A further means for tuning the circuit is provided by a capacitive bridge including the capacitor 31. The points of connection 39 are also adjustable along the conductors 21.

Any suitable antenna system such as a dipole 4| may be symmetrically connected to the conductors ill at advantageous points for efficient transfer of energy to the electron discharge device.

High frequency energy collected on the antenna and impressed out of phase upon the filaments 1 may be detected through the well known action of the Barkhausen-Kurz tube elements. The high positive potential which is im- 55 pressed upon the grid produces an oscillatory action upon the electrons which are emitted from the filaments. Those of the electrons which have suflicient velocity to be projected through the mesh of the grid are thereafter retarded so that many of them do not reach the inner wall of the plate but are attracted back again to the grid and to the cathode. The radio frequency energy impressed upon the cathode produces a varying difference of potential between the cathode and the other electrodes such that the direct current component between the grid and the cathode is likewise varied. By virtue of the by-pass capacitor 43, one side of which is grounded, the plates are caused to operate substantially at grounded radio-frequency potential. Demodulation of the received energy is obtained in the output circuit, which includes the primary 9 of the transformer The detected signal may, therefore, be utilized in any desired manner.

Referring now to Fig. 2, I show a modification of my invention in which the two triode systems though mounted side by side within one envelope are sufficiently separated from one another so that complete independence of one triode from the other may be maintained. In certain instances it may be desirable to impress difierent voltages upon the two grids and upon the two plates in order to obtain a satisfactory balance between the two paths of my push-pull system, as will hereinafter appear.

This may be readily accomplished in accordance with the circuit arrangements shown in Fig. 2. The cylindrical plates 45 may be mounted in any suitable manner in accordance with conventional tube design. Within the plates and symmetrically disposed are the usual electrodes including grids 5 and filaments the same as are shown in Fig. 1. In this instance, however, I have shown by way of illustration how the filaments may be connected in parallel instead of in series. The filament potential is here derived from a battery 41, one side of which is grounded and the other side of which is connected to a rheostat 29. From the rheostat direct current is fed to the filaments through a suitable choke 3| and a bridging member 45.

The Lecher-wire system of which the filal ments are component parts extends transversely across the cylindrical walls of the vacuum tube envelope. The antenna 4| is adjustably connected to the wires 21. Both of the bridging members 49 and 5| are arranged to be moved into proper position for tuning the circuit so as to produce loops of radio frequency waves on the filaments 1. The return circuit for the filament heating current is led through a center tap on the bridge member 5| and thence through a suitable choke 3|a to ground. The high voltage power supply for the grids may be obtained from the source I1, the two sides of which are connected respectively to the terminals of a potentiometer 5a. This potentiometer, however, has two taps |3a and |3b each leading through a different path of a push pull circuit including in each path a primary winding of a transformer 53, and thence to its respective grid 5. The taps 3a and I31), being independent of one another, may be so adjusted as to impress any desired voltages upon the grids 5 independently of one another.

In like manner the plate voltages impressed upon the two plates 45 may be adjusted each independently of the other, the taps 2|a and 2|b on the potentiometer 230. being used for this purpose. The potentiometer 23a is connected between the positive side of the battery 41 and ground and hence supplies any suitable positive or negative bias with respect to the mean potential of 5 the filaments. Two grounded by-pass condensers 43a and 43b are used in connection with the respective plate circuit leads to provide a balanced push pull anode circuit. These serve the same purposes as that of the capacitor 43 10 indicated in Fig. 1. The secondary of the transformer 53 is connected to any desired utilization circuit.

The action of the receiving system for detecting ultra high frequency modulated waves or in- 15 termittent waves is substantially the same whether the diagram of Fig. 2 or that of Fig. 1 is followed.

Numerous advantages are obtained from the carrying out of my invention as herein shown and described. The impedance matching of different portions of the system is facilitated by the fact that the parallel wires 21 and 33 of the Lecher-wire system are disposed very close to one another and, within the tube envelope, 25 there is a tapering outwardly and inwardly of the connections to the filaments. This arrangement lends itself to a greatly improved performance of the system since it is easy to obtain symmetry of the electrical characteristics on the 30 two sides of the antenna and transmission lines as well as through the tube elements. The length of the tapered sections as well as the diameter of the conductors used are so chosen as to obtain a rough sort of impedance match before other adjustments are made. The adjustment of the bridging members 35, 3?, 49 and 5| along the Lecher-wire system facilitates the matter of building up radio frequency voltage loops upon the filaments. The impedance matching is further facilitated by the adjustable connections of the antenna system along the Lecher-wire system.

It has been found of considerable advantage to apply the radio frequency signal to the filament rather than to the plate because the filament has smaller electrostatic capacity and, therefore, reduces the load upon the line. It is necessary, of course, that the filament supports within the envelope be such that no large amount of capacity is added to that of the filament itself. A higher amplitude of the voltage loop at the filament is thus obtained.

Although I have herein shown two specific embodiments of my invention, it is to be understood that these are merely illustrative and that modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim as my invention:

1. A short wave radio receiving system comprising an antenna, a thermionic push-pull detector and a utilization circuit, said detector having all of its electrodes enclosed in one envelope, said electrodes comprising independent 65 cylindrical anodes and each anode having in cooperation therewith an accelerating electrode and an electron emitting cathode, an electric heating source connected with said cathodes, means including independent connections between each of said cathodes and separate portions of said antenna whereby said cathodes are included in said antenna and radio frequency energy may be impressed on said cathodes in out of phase relation, and means including a 7 suitable energy source for so polarizing said electrodes with respect to one another as to cause said system to detect and to utilize theenergy impressed on said antenna.

2. In a device for short wave reception, an electron tube comprising a plurality of independent sets of cooperating electrodes each set including a cathode, an anode and an accelerating electrode, a radio energy collecting device, meansincluding a bi-filar transmission line for supplying energy from said collecting device in out of phase relation to the respective cathodes of two of said sets and for causing said sets to operate in a push-pull manner, an output circuit connected to both of said accelerating electrodes jointly, means for supplying operating potentials across said electrodes, means for operating said anodes at substantially a grounded radio-frequency potential, and means for supplying heating energy through said transmission line to said cathodes.

3. A short wave radio receiving system comprising an antenna, a two-conductor transmission line connected to separate portions of said antenna and proportioned to derive energy therefrom which is impressed upon the respective conductors in out of phase relation, an electron discharge tube of the Barkhausen-Kurz type and having two independent sets of electrodes, each set including a cathode, a plate and a grid, the cathode of each set being connected to one of said conductors respectively, means for supplying heating energy through said conductors to said cathodes, an output circuit connected to both of the two accelerating electrodes in common, capacitive coupling means for causing said anodes to be maintained substantially at grounded radio frequency potential, and means including a short circuiting conductor disposed across said conductors at one point and a capacitor disposed thereacross at another point for so tuning the circuit of said antenna, said cathode and said two-conductor transmission line as to establish a voltage loop at substantially the middle of each cathode.

4. A short wave radio receiving system comprising an antenna, a Lecher-wire transmission device connected to said antenna, an electron discharge tube comprising two independent sets of electrodes, each set including a cathode, a plate and a grid, each of said cathodes being serially connected into said transmission device, means for so bridging said transmission device conductively near one end thereof and capacitively near the other end thereof as to produce standing waves of energy derived from said antenna and so that loops of said standing waves are maintained on said cathodes, and means for so polarizing the electrodes of said electron discharge tube with respect to one another that said tube iscaused to function as a detector.

5. A short wave radio receiving system comprising an antenna, a thermionic balanced de tector and a utilization circuit, said detector comprising two sets of electrodes within one envelope, each filament of said electrodes being disposed axially of its set and having lead-in conductors providing circuit connections for the terminals thereof exteriorly of said envelope, a Lecher-wire system connecting said antenna with two of said lead-in conductors, and means including a shorting bar tunably disposed in contact with two others of said lead-in conductors for setting up standing loops of radio waves at points midway of each filament.

6. A system in accordance with claim 5 and having a filament heating source connected to said Lecher-wire system.

7. A system in accordance with claim 5 and having means including an energy source and suitable impedances so connected to said Lecher-wire system as to supply filament heating current thereto while avoiding undesirable dissipation of radio frequency waves impressed thereon.

8. A short wave radio receiving system comprising in combination, an electric discharge device having a pair of spaced substantially parallel straight-wire filaments, a pair of Lecherwire conductors each including one of said filaments and extending therefrom at opposite ends, filter means for supplying filamentary heating current through said wires, means providing adjustable bridging current paths directly between said conductors on opposite sides of said filaments, at least one of said paths being conducting, and a dipole antenna adjustably connected with said conductors on one side of the filaments.

9. In a short wave radio receiving system, the combination of a pair of Lecher-wire conductors, each of said conductors including a straight-wire filament, an anode electrode associated with each filament and a grid electrode interposed between each filament and its anode whereby a pair of triodes is provided, means for operating said triodes as an oscillator with relatively high positive grid bias and low anodecathode potential, means providing an adjustable bridging connection between said conductors on opposite sides of said filaments whereby said Lecher-wire system is tunable, and a dipole antenna having portions connected each with one of said conductors at adjacent points on the one side of said filaments.

RENE A. BRADEN. 

